<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>perldtrace - Perl&#39;s support for DTrace - Perldoc Browser</title>
    <link rel="search" href="https://perldoc.perl.org/opensearch.xml" type="application/opensearchdescription+xml" title="Perldoc Browser">
    <link rel="canonical" href="https://perldoc.perl.org/perldtrace">
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css" integrity="sha384-JcKb8q3iqJ61gNV9KGb8thSsNjpSL0n8PARn9HuZOnIxN0hoP+VmmDGMN5t9UJ0Z" crossorigin="anonymous">
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/10.5.0/styles/stackoverflow-light.min.css" integrity="sha512-cG1IdFxqipi3gqLmksLtuk13C+hBa57a6zpWxMeoY3Q9O6ooFxq50DayCdm0QrDgZjMUn23z/0PMZlgft7Yp5Q==" crossorigin="anonymous" />
    <style>
      body {
        background: #f4f4f5;
        color: #020202;
      }
      .navbar-dark {
        background-image: -webkit-linear-gradient(top, #005f85 0, #002e49 100%);
        background-image: -o-linear-gradient(top, #005f85 0, #002e49 100%);
        background-image: linear-gradient(to bottom, #005f85 0, #002e49 100%);
        filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#ff005f85', endColorstr='#ff002e49', GradientType=0);
        background-repeat: repeat-x;
      }
      .navbar-dark .navbar-nav .nav-link,
      .navbar-dark .navbar-nav .nav-link:focus { color: #fff }
      .navbar-dark .navbar-nav .nav-link:hover { color: #ffef68 }
      #wrapperlicious {
        margin: 0 auto;
        font: 0.9em 'Helvetica Neue', Helvetica, sans-serif;
        font-weight: normal;
        line-height: 1.5em;
        margin: 0;
        padding: 0;
      }
      #wrapperlicious h1 { font-size: 1.5em }
      #wrapperlicious h2 { font-size: 1.3em }
      #wrapperlicious h3 { font-size: 1.1em }
      #wrapperlicious h4 { font-size: 0.9em }
      #wrapperlicious h1, #wrapperlicious h2, #wrapperlicious h3,
      #wrapperlicious h4, #wrapperlicious dt {
        color: #020202;
        margin-top: 1em;
        margin-bottom: 1em;
        position: relative;
        font-weight: bold;
      }
      #wrapperlicious a { color: inherit; text-decoration: underline }
      #wrapperlicious #toc { text-decoration: none }
      #wrapperlicious a:hover { color: #2a2a2a }
      #wrapperlicious a img { border: 0 }
      #wrapperlicious :not(pre) > code {
        color: inherit;
        background-color: rgba(0, 0, 0, 0.04);
        border-radius: 3px;
        font: 0.9em Consolas, Menlo, Monaco, monospace;
        padding: 0.3em;
      }
      #wrapperlicious dd {
        margin: 0;
        margin-left: 2em;
      }
      #wrapperlicious dt {
        color: #2a2a2a;
        font-weight: bold;
        margin-left: 0.9em;
      }
      #wrapperlicious p {
        margin-bottom: 1em;
        margin-top: 1em;
      }
      #wrapperlicious li > p {
        margin-bottom: 0;
        margin-top: 0;
      }
      #wrapperlicious pre {
        border: 1px solid #c1c1c1;
        border-radius: 3px;
        font: 100% Consolas, Menlo, Monaco, monospace;
        margin-bottom: 1em;
        margin-top: 1em;
      }
      #wrapperlicious pre > code {
        display: block;
        background-color: #f6f6f6;
        font: 0.9em Consolas, Menlo, Monaco, monospace;
        line-height: 1.5em;
        text-align: left;
        white-space: pre;
        padding: 1em;
      }
      #wrapperlicious dl, #wrapperlicious ol, #wrapperlicious ul {
        margin-bottom: 1em;
        margin-top: 1em;
      }
      #wrapperlicious ul {
        list-style-type: square;
      }
      #wrapperlicious ul ul {
        margin-bottom: 0px;
        margin-top: 0px;
      }
      #footer {
        font-size: 0.8em;
        padding-top: 0.5em;
        text-align: center;
      }
      #more {
        display: inline;
        font-size: 0.8em;
      }
      #perldocdiv {
        background-color: #fff;
        border: 1px solid #c1c1c1;
        border-bottom-left-radius: 5px;
        border-bottom-right-radius: 5px;
        margin-left: auto;
        margin-right: auto;
        padding: 3em;
        padding-top: 1em;
        max-width: 960px;
      }
      #moduleversion { float: right }
      #wrapperlicious .leading-notice {
        font-style: italic;
        padding-left: 1em;
        margin-top: 1em;
        margin-bottom: 1em;
      }
      #wrapperlicious .permalink {
        display: none;
        left: -0.75em;
        position: absolute;
        padding-right: 0.25em;
        text-decoration: none;
      }
      #wrapperlicious h1:hover .permalink, #wrapperlicious h2:hover .permalink,
      #wrapperlicious h3:hover .permalink, #wrapperlicious h4:hover .permalink,
      #wrapperlicious dt:hover .permalink {
        display: block;
      }
    </style>
    <!-- Global site tag (gtag.js) - Google Analytics -->
    <script async src="https://www.googletagmanager.com/gtag/js?id=G-KVNWBNT5FB"></script>
    <script>
      window.dataLayer = window.dataLayer || [];
      function gtag(){dataLayer.push(arguments);}
      gtag('js', new Date());

      gtag('config', 'G-KVNWBNT5FB');
      gtag('config', 'UA-50555-3');
    </script>
  </head>
  <body>
    <nav class="navbar navbar-expand-md navbar-dark bg-dark justify-content-between">
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>
  <a class="navbar-brand" href="https://perldoc.perl.org/">Perldoc Browser</a>
  <div class="collapse navbar-collapse" id="navbarNav">
    <ul class="navbar-nav mr-auto">
      <li class="nav-item dropdown text-nowrap">
        <a class="nav-link dropdown-toggle" href="perldtrace.html#" id="dropdownlink-stable" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">5.35.0</a>
        <div class="dropdown-menu" aria-labelledby="dropdownlink-stable">
          <a class="dropdown-item" href="https://perldoc.perl.org/perldtrace">Latest</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.38.2/perldtrace">5.38.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.38.1/perldtrace">5.38.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.38.0/perldtrace">5.38.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.36.3/perldtrace">5.36.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.36.2/perldtrace">5.36.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.36.1/perldtrace">5.36.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.36.0/perldtrace">5.36.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.34.3/perldtrace">5.34.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.34.2/perldtrace">5.34.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.34.1/perldtrace">5.34.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.34.0/perldtrace">5.34.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.32.1/perldtrace">5.32.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.32.0/perldtrace">5.32.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.30.3/perldtrace">5.30.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.30.2/perldtrace">5.30.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.30.1/perldtrace">5.30.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.30.0/perldtrace">5.30.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.28.3/perldtrace">5.28.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.28.2/perldtrace">5.28.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.28.1/perldtrace">5.28.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.28.0/perldtrace">5.28.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.26.3/perldtrace">5.26.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.26.2/perldtrace">5.26.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.26.1/perldtrace">5.26.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.26.0/perldtrace">5.26.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.24.4/perldtrace">5.24.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.24.3/perldtrace">5.24.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.24.2/perldtrace">5.24.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.24.1/perldtrace">5.24.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.24.0/perldtrace">5.24.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.22.4/perldtrace">5.22.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.22.3/perldtrace">5.22.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.22.2/perldtrace">5.22.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.22.1/perldtrace">5.22.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.22.0/perldtrace">5.22.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.20.3/perldtrace">5.20.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.20.2/perldtrace">5.20.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.20.1/perldtrace">5.20.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.20.0/perldtrace">5.20.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.18.4/perldtrace">5.18.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.18.3/perldtrace">5.18.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.18.2/perldtrace">5.18.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.18.1/perldtrace">5.18.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.18.0/perldtrace">5.18.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.16.3/perldtrace">5.16.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.16.2/perldtrace">5.16.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.16.1/perldtrace">5.16.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.16.0/perldtrace">5.16.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.14.4/perldtrace">5.14.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.14.3/perldtrace">5.14.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.14.2/perldtrace">5.14.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.14.1/perldtrace">5.14.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.14.0/perldtrace">5.14.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.5/perldtrace">5.12.5</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.4/perldtrace">5.12.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.3/perldtrace">5.12.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.2/perldtrace">5.12.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.1/perldtrace">5.12.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.0/perldtrace">5.12.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.10.1/perldtrace">5.10.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.10.0/perldtrace">5.10.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.9/perldtrace">5.8.9</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.8/perldtrace">5.8.8</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.7/perldtrace">5.8.7</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.6/perldtrace">5.8.6</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.5/perldtrace">5.8.5</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.4/perldtrace">5.8.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.3/perldtrace">5.8.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.2/perldtrace">5.8.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.1/perldtrace">5.8.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.0/perldtrace">5.8.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.6.2/perldtrace">5.6.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.6.1/perldtrace">5.6.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.6.0/perldtrace">5.6.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.005_04/perldtrace">5.005_04</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.005_03/perldtrace">5.005_03</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.005_02/perldtrace">5.005_02</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.005_01/perldtrace">5.005_01</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.005/perldtrace">5.005</a>
        </div>
      </li>
      <li class="nav-item dropdown text-nowrap">
        <a class="nav-link dropdown-toggle" href="perldtrace.html#" id="dropdownlink-dev" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Dev</a>
        <div class="dropdown-menu" aria-labelledby="dropdownlink-dev">
          <a class="dropdown-item" href="https://perldoc.perl.org/blead/perldtrace">blead</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.6/perldtrace">5.39.6</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.5/perldtrace">5.39.5</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.4/perldtrace">5.39.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.3/perldtrace">5.39.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.2/perldtrace">5.39.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.1/perldtrace">5.39.1</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.38.0-RC2/perldtrace">5.38.0-RC2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.38.0-RC1/perldtrace">5.38.0-RC1</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.11/perldtrace">5.37.11</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.10/perldtrace">5.37.10</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.9/perldtrace">5.37.9</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.8/perldtrace">5.37.8</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.7/perldtrace">5.37.7</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.6/perldtrace">5.37.6</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.5/perldtrace">5.37.5</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.4/perldtrace">5.37.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.3/perldtrace">5.37.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.2/perldtrace">5.37.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.1/perldtrace">5.37.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.0/perldtrace">5.37.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.11/perldtrace">5.35.11</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.10/perldtrace">5.35.10</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.9/perldtrace">5.35.9</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.8/perldtrace">5.35.8</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.7/perldtrace">5.35.7</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.6/perldtrace">5.35.6</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.5/perldtrace">5.35.5</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.4/perldtrace">5.35.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.3/perldtrace">5.35.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.2/perldtrace">5.35.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.1/perldtrace">5.35.1</a>
          <a class="dropdown-item active" href="perldtrace.html">5.35.0</a>
        </div>
      </li>
      <li class="nav-item dropdown text-nowrap">
        <a class="nav-link dropdown-toggle" href="perldtrace.html#" id="dropdownlink-nav" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Documentation</a>
        <div class="dropdown-menu" aria-labelledby="dropdownlink-nav">
          <a class="dropdown-item" href="perl.html">Perl</a>
          <a class="dropdown-item" href="perlintro.html">Intro</a>
          <a class="dropdown-item" href="perl.html#Tutorials">Tutorials</a>
          <a class="dropdown-item" href="perlfaq.html">FAQs</a>
          <a class="dropdown-item" href="perl.html#Reference-Manual">Reference</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="perlop.html">Operators</a>
          <a class="dropdown-item" href="functions.html">Functions</a>
          <a class="dropdown-item" href="variables.html">Variables</a>
          <a class="dropdown-item" href="modules.html">Modules</a>
          <a class="dropdown-item" href="perlutil.html">Utilities</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="perlcommunity.html">Community</a>
          <a class="dropdown-item" href="perlhist.html">History</a>
        </div>
      </li>
    </ul>
    <ul class="navbar-nav">
      <script>
        function set_expand (expand) {
          var perldocdiv = document.getElementById('perldocdiv');
          var width = window.getComputedStyle(perldocdiv).getPropertyValue('max-width');
          var expanded = (width == '' || width == 'none') ? true : false;
          if (expand === null) {
            expand = !expanded;
          }
          if ((expand && !expanded) || (!expand && expanded)) {
            perldocdiv.style.setProperty('max-width', expand ? 'none' : '960px');
            var button_classlist = document.getElementById('content-expand-button').classList;
            if (expand) {
              button_classlist.add('btn-light');
              button_classlist.remove('btn-outline-light');
            } else {
              button_classlist.add('btn-outline-light');
              button_classlist.remove('btn-light');
            }
          }
          return expand;
        }
        function toggle_expand () {
          var expand = set_expand(null);
          document.cookie = 'perldoc_expand=' + (expand ? 1 : 0) + '; path=/; expires=Tue, 19 Jan 2038 03:14:07 UTC';
        }
        function read_expand () {
          return document.cookie.split(';').some(function (item) { return item.indexOf('perldoc_expand=1') >= 0 });
        }
        if (document.readyState === 'loading') {
          document.addEventListener('DOMContentLoaded', function () {
            if (read_expand()) {
              set_expand(true);
            }
          });
        } else if (read_expand()) {
          set_expand(true);
        }
      </script>
      <button id="content-expand-button" type="button" class="btn btn-outline-light d-none d-lg-inline-block mr-2" onclick="toggle_expand()">Expand</button>
    <ul>
    <form class="form-inline" method="get" action="https://perldoc.perl.org/5.35.0/search">
      <input class="form-control mr-3" type="search" name="q" placeholder="Search" aria-label="Search">
    </form>
  </div>
</nav>

    <div id="wrapperlicious" class="container-fluid">
      <div id="perldocdiv">
        <div id="links">
          <a href="perldtrace.html">perldtrace</a>
          <div id="more">
            (<a href="perldtrace.txt">source</a>,
            <a href="https://metacpan.org/pod/perldtrace">CPAN</a>)
          </div>
        </div>
        <div class="leading-notice">
          You are viewing the version of this documentation from Perl 5.35.0.
            This is a development version of Perl.
        </div>
        <h1><a id="toc">CONTENTS</a></h1>
                  <ul>
              <li>
                <a class="text-decoration-none" href="perldtrace.html#NAME">NAME</a>
              </li>
              <li>
                <a class="text-decoration-none" href="perldtrace.html#SYNOPSIS">SYNOPSIS</a>
              </li>
              <li>
                <a class="text-decoration-none" href="perldtrace.html#DESCRIPTION">DESCRIPTION</a>
              </li>
              <li>
                <a class="text-decoration-none" href="perldtrace.html#HISTORY">HISTORY</a>
              </li>
              <li>
                <a class="text-decoration-none" href="perldtrace.html#PROBES">PROBES</a>
              </li>
              <li>
                <a class="text-decoration-none" href="perldtrace.html#EXAMPLES">EXAMPLES</a>
              </li>
              <li>
                <a class="text-decoration-none" href="perldtrace.html#REFERENCES">REFERENCES</a>
              </li>
              <li>
                <a class="text-decoration-none" href="perldtrace.html#SEE-ALSO">SEE ALSO</a>
              </li>
              <li>
                <a class="text-decoration-none" href="perldtrace.html#AUTHORS">AUTHORS</a>
              </li>
          </ul>

      <h1 id="NAME"><a class="permalink" href="perldtrace.html#NAME">#</a>NAME</h1>

<p>perldtrace - Perl&#39;s support for DTrace</p>

<h1 id="SYNOPSIS"><a class="permalink" href="perldtrace.html#SYNOPSIS">#</a>SYNOPSIS</h1>

<pre><code># dtrace -Zn &#39;perl::sub-entry, perl::sub-return { trace(copyinstr(arg0)) }&#39;
dtrace: description &#39;perl::sub-entry, perl::sub-return &#39; matched 10 probes

# perl -E &#39;sub outer { inner(@_) } sub inner { say shift } outer(&quot;hello&quot;)&#39;
hello

(dtrace output)
CPU     ID                    FUNCTION:NAME
  0  75915       Perl_pp_entersub:sub-entry   BEGIN
  0  75915       Perl_pp_entersub:sub-entry   import
  0  75922      Perl_pp_leavesub:sub-return   import
  0  75922      Perl_pp_leavesub:sub-return   BEGIN
  0  75915       Perl_pp_entersub:sub-entry   outer
  0  75915       Perl_pp_entersub:sub-entry   inner
  0  75922      Perl_pp_leavesub:sub-return   inner
  0  75922      Perl_pp_leavesub:sub-return   outer</code></pre>

<h1 id="DESCRIPTION"><a class="permalink" href="perldtrace.html#DESCRIPTION">#</a>DESCRIPTION</h1>

<p>DTrace is a framework for comprehensive system- and application-level tracing. Perl is a DTrace <i>provider</i>, meaning it exposes several <i>probes</i> for instrumentation. You can use these in conjunction with kernel-level probes, as well as probes from other providers such as MySQL, in order to diagnose software defects, or even just your application&#39;s bottlenecks.</p>

<p>Perl must be compiled with the <code>-Dusedtrace</code> option in order to make use of the provided probes. While DTrace aims to have no overhead when its instrumentation is not active, Perl&#39;s support itself cannot uphold that guarantee, so it is built without DTrace probes under most systems. One notable exception is that Mac OS X ships a <i>/usr/bin/perl</i> with DTrace support enabled.</p>

<h1 id="HISTORY"><a class="permalink" href="perldtrace.html#HISTORY">#</a>HISTORY</h1>

<dl>

<dt id="5.10.1"><a class="permalink" href="perldtrace.html#5.10.1">#</a><a id="5"></a><a id="pod5.10.1"></a>5.10.1</dt>
<dd>

<p>Perl&#39;s initial DTrace support was added, providing <code>sub-entry</code> and <code>sub-return</code> probes.</p>

</dd>
<dt id="5.14.0"><a class="permalink" href="perldtrace.html#5.14.0">#</a><a id="51"></a><a id="pod5.14.0"></a>5.14.0</dt>
<dd>

<p>The <code>sub-entry</code> and <code>sub-return</code> probes gain a fourth argument: the package name of the function.</p>

</dd>
<dt id="5.16.0"><a class="permalink" href="perldtrace.html#5.16.0">#</a><a id="52"></a><a id="pod5.16.0"></a>5.16.0</dt>
<dd>

<p>The <code>phase-change</code> probe was added.</p>

</dd>
<dt id="5.18.0"><a class="permalink" href="perldtrace.html#5.18.0">#</a><a id="53"></a><a id="pod5.18.0"></a>5.18.0</dt>
<dd>

<p>The <code>op-entry</code>, <code>loading-file</code>, and <code>loaded-file</code> probes were added.</p>

</dd>
</dl>

<h1 id="PROBES"><a class="permalink" href="perldtrace.html#PROBES">#</a>PROBES</h1>

<dl>

<dt id="sub-entry(SUBNAME,-FILE,-LINE,-PACKAGE)"><a class="permalink" href="perldtrace.html#sub-entry(SUBNAME,-FILE,-LINE,-PACKAGE)">#</a><a id="sub"></a><a id="sub-entry-SUBNAME-FILE-LINE-PACKAGE"></a>sub-entry(SUBNAME, FILE, LINE, PACKAGE)</dt>
<dd>

<p>Traces the entry of any subroutine. Note that all of the variables refer to the subroutine that is being invoked; there is currently no way to get ahold of any information about the subroutine&#39;s <i>caller</i> from a DTrace action.</p>

<pre><code>:*perl*::sub-entry {
    printf(&quot;%s::%s entered at %s line %d\n&quot;,
          copyinstr(arg3), copyinstr(arg0), copyinstr(arg1), arg2);
}</code></pre>

</dd>
<dt id="sub-return(SUBNAME,-FILE,-LINE,-PACKAGE)"><a class="permalink" href="perldtrace.html#sub-return(SUBNAME,-FILE,-LINE,-PACKAGE)">#</a><a id="sub1"></a><a id="sub-return-SUBNAME-FILE-LINE-PACKAGE"></a>sub-return(SUBNAME, FILE, LINE, PACKAGE)</dt>
<dd>

<p>Traces the exit of any subroutine. Note that all of the variables refer to the subroutine that is returning; there is currently no way to get ahold of any information about the subroutine&#39;s <i>caller</i> from a DTrace action.</p>

<pre><code>:*perl*::sub-return {
    printf(&quot;%s::%s returned at %s line %d\n&quot;,
          copyinstr(arg3), copyinstr(arg0), copyinstr(arg1), arg2);
}</code></pre>

</dd>
<dt id="phase-change(NEWPHASE,-OLDPHASE)"><a class="permalink" href="perldtrace.html#phase-change(NEWPHASE,-OLDPHASE)">#</a><a id="phase"></a><a id="phase-change-NEWPHASE-OLDPHASE"></a>phase-change(NEWPHASE, OLDPHASE)</dt>
<dd>

<p>Traces changes to Perl&#39;s interpreter state. You can internalize this as tracing changes to Perl&#39;s <code>${^GLOBAL_PHASE}</code> variable, especially since the values for <code>NEWPHASE</code> and <code>OLDPHASE</code> are the strings that <code>${^GLOBAL_PHASE}</code> reports.</p>

<pre><code>:*perl*::phase-change {
    printf(&quot;Phase changed from %s to %s\n&quot;,
        copyinstr(arg1), copyinstr(arg0));
}</code></pre>

</dd>
<dt id="op-entry(OPNAME)"><a class="permalink" href="perldtrace.html#op-entry(OPNAME)">#</a><a id="op"></a><a id="op-entry-OPNAME"></a>op-entry(OPNAME)</dt>
<dd>

<p>Traces the execution of each opcode in the Perl runloop. This probe is fired before the opcode is executed. When the Perl debugger is enabled, the DTrace probe is fired <i>after</i> the debugger hooks (but still before the opcode itself is executed).</p>

<pre><code>:*perl*::op-entry {
    printf(&quot;About to execute opcode %s\n&quot;, copyinstr(arg0));
}</code></pre>

</dd>
<dt id="loading-file(FILENAME)"><a class="permalink" href="perldtrace.html#loading-file(FILENAME)">#</a><a id="loading"></a><a id="loading-file-FILENAME"></a>loading-file(FILENAME)</dt>
<dd>

<p>Fires when Perl is about to load an individual file, whether from <code>use</code>, <code>require</code>, or <code>do</code>. This probe fires before the file is read from disk. The filename argument is converted to local filesystem paths instead of providing <code>Module::Name</code>-style names.</p>

<pre><code>:*perl*:loading-file {
    printf(&quot;About to load %s\n&quot;, copyinstr(arg0));
}</code></pre>

</dd>
<dt id="loaded-file(FILENAME)"><a class="permalink" href="perldtrace.html#loaded-file(FILENAME)">#</a><a id="loaded"></a><a id="loaded-file-FILENAME"></a>loaded-file(FILENAME)</dt>
<dd>

<p>Fires when Perl has successfully loaded an individual file, whether from <code>use</code>, <code>require</code>, or <code>do</code>. This probe fires after the file is read from disk and its contents evaluated. The filename argument is converted to local filesystem paths instead of providing <code>Module::Name</code>-style names.</p>

<pre><code>:*perl*:loaded-file {
    printf(&quot;Successfully loaded %s\n&quot;, copyinstr(arg0));
}</code></pre>

</dd>
</dl>

<h1 id="EXAMPLES"><a class="permalink" href="perldtrace.html#EXAMPLES">#</a>EXAMPLES</h1>

<dl>

<dt id="Most-frequently-called-functions"><a class="permalink" href="perldtrace.html#Most-frequently-called-functions">#</a><a id="Most"></a>Most frequently called functions</dt>
<dd>

<pre><code class="plaintext"># dtrace -qZn &#39;sub-entry { @[strjoin(strjoin(copyinstr(arg3),&quot;::&quot;),copyinstr(arg0))] = count() } END {trunc(@, 10)}&#39;

Class::MOP::Attribute::slots                                    400
Try::Tiny::catch                                                411
Try::Tiny::try                                                  411
Class::MOP::Instance::inline_slot_access                        451
Class::MOP::Class::Immutable::Trait:::around                    472
Class::MOP::Mixin::AttributeCore::has_initializer               496
Class::MOP::Method::Wrapped::__ANON__                           544
Class::MOP::Package::_package_stash                             737
Class::MOP::Class::initialize                                  1128
Class::MOP::get_metaclass_by_name                              1204</code></pre>

</dd>
<dt id="Trace-function-calls"><a class="permalink" href="perldtrace.html#Trace-function-calls">#</a><a id="Trace"></a>Trace function calls</dt>
<dd>

<pre><code class="plaintext"># dtrace -qFZn &#39;sub-entry, sub-return { trace(copyinstr(arg0)) }&#39;

0  -&gt; Perl_pp_entersub                        BEGIN
0  &lt;- Perl_pp_leavesub                        BEGIN
0  -&gt; Perl_pp_entersub                        BEGIN
0    -&gt; Perl_pp_entersub                      import
0    &lt;- Perl_pp_leavesub                      import
0  &lt;- Perl_pp_leavesub                        BEGIN
0  -&gt; Perl_pp_entersub                        BEGIN
0    -&gt; Perl_pp_entersub                      dress
0    &lt;- Perl_pp_leavesub                      dress
0    -&gt; Perl_pp_entersub                      dirty
0    &lt;- Perl_pp_leavesub                      dirty
0    -&gt; Perl_pp_entersub                      whiten
0    &lt;- Perl_pp_leavesub                      whiten
0  &lt;- Perl_dounwind                           BEGIN</code></pre>

</dd>
<dt id="Function-calls-during-interpreter-cleanup"><a class="permalink" href="perldtrace.html#Function-calls-during-interpreter-cleanup">#</a><a id="Function"></a>Function calls during interpreter cleanup</dt>
<dd>

<pre><code># dtrace -Zn &#39;phase-change /copyinstr(arg0) == &quot;END&quot;/ { self-&gt;ending = 1 } sub-entry /self-&gt;ending/ { trace(copyinstr(arg0)) }&#39;

CPU     ID                    FUNCTION:NAME
  1  77214       Perl_pp_entersub:sub-entry   END
  1  77214       Perl_pp_entersub:sub-entry   END
  1  77214       Perl_pp_entersub:sub-entry   cleanup
  1  77214       Perl_pp_entersub:sub-entry   _force_writable
  1  77214       Perl_pp_entersub:sub-entry   _force_writable</code></pre>

</dd>
<dt id="System-calls-at-compile-time"><a class="permalink" href="perldtrace.html#System-calls-at-compile-time">#</a><a id="System"></a>System calls at compile time</dt>
<dd>

<pre><code># dtrace -qZn &#39;phase-change /copyinstr(arg0) == &quot;START&quot;/ { self-&gt;interesting = 1 } phase-change /copyinstr(arg0) == &quot;RUN&quot;/ { self-&gt;interesting = 0 } syscall::: /self-&gt;interesting/ { @[probefunc] = count() } END { trunc(@, 3) }&#39;

lseek                                                           310
read                                                            374
stat64                                                         1056</code></pre>

</dd>
<dt id="Perl-functions-that-execute-the-most-opcodes"><a class="permalink" href="perldtrace.html#Perl-functions-that-execute-the-most-opcodes">#</a><a id="Perl"></a>Perl functions that execute the most opcodes</dt>
<dd>

<pre><code># dtrace -qZn &#39;sub-entry { self-&gt;fqn = strjoin(copyinstr(arg3), strjoin(&quot;::&quot;, copyinstr(arg0))) } op-entry /self-&gt;fqn != &quot;&quot;/ { @[self-&gt;fqn] = count() } END { trunc(@, 3) }&#39;

warnings::unimport                                             4589
Exporter::Heavy::_rebuild_cache                                5039
Exporter::import                                              14578</code></pre>

</dd>
</dl>

<h1 id="REFERENCES"><a class="permalink" href="perldtrace.html#REFERENCES">#</a>REFERENCES</h1>

<dl>

<dt id="DTrace-Dynamic-Tracing-Guide"><a class="permalink" href="perldtrace.html#DTrace-Dynamic-Tracing-Guide">#</a><a id="DTrace"></a>DTrace Dynamic Tracing Guide</dt>
<dd>

<p><a href="http://dtrace.org/guide/preface.html">http://dtrace.org/guide/preface.html</a></p>

</dd>
<dt id="DTrace:-Dynamic-Tracing-in-Oracle-Solaris,-Mac-OS-X-and-FreeBSD"><a class="permalink" href="perldtrace.html#DTrace:-Dynamic-Tracing-in-Oracle-Solaris,-Mac-OS-X-and-FreeBSD">#</a><a id="DTrace1"></a><a id="DTrace:-Dynamic-Tracing-in-Oracle-Solaris-Mac-OS-X-and-FreeBSD"></a>DTrace: Dynamic Tracing in Oracle Solaris, Mac OS X and FreeBSD</dt>
<dd>

<p><a href="https://www.amazon.com/DTrace-Dynamic-Tracing-Solaris-FreeBSD/dp/0132091518/">https://www.amazon.com/DTrace-Dynamic-Tracing-Solaris-FreeBSD/dp/0132091518/</a></p>

</dd>
</dl>

<h1 id="SEE-ALSO"><a class="permalink" href="perldtrace.html#SEE-ALSO">#</a><a id="SEE"></a>SEE ALSO</h1>

<dl>

<dt id="Devel::DTrace::Provider"><a class="permalink" href="perldtrace.html#Devel::DTrace::Provider">#</a><a id="Devel"></a><a href="./Devel::DTrace::Provider.html">Devel::DTrace::Provider</a></dt>
<dd>

<p>This CPAN module lets you create application-level DTrace probes written in Perl.</p>

</dd>
</dl>

<h1 id="AUTHORS"><a class="permalink" href="perldtrace.html#AUTHORS">#</a>AUTHORS</h1>

<p>Shawn M Moore <code>sartak@gmail.com</code></p>


      </div>
      <div id="footer">
        <p>Perldoc Browser is maintained by Dan Book (<a href="https://metacpan.org/author/DBOOK">DBOOK</a>). Please contact him via the <a href="https://github.com/Grinnz/perldoc-browser/issues">GitHub issue tracker</a> or <a href="mailto:dbook@cpan.org">email</a> regarding any issues with the site itself, search, or rendering of documentation.</p>

<p>The Perl documentation is maintained by the Perl 5 Porters in the development of Perl. Please contact them via the <a href="https://github.com/Perl/perl5/issues">Perl issue tracker</a>, the <a href="https://lists.perl.org/list/perl5-porters.html">mailing list</a>, or <a href="https://kiwiirc.com/client/irc.perl.org/p5p">IRC</a> to report any issues with the contents or format of the documentation.</p>


      </div>
    </div>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.slim.min.js" integrity="sha512-/DXTXr6nQodMUiq+IUJYCt2PPOUjrHJ9wFrqpJ3XkgPNOZVfMok7cRw6CSxyCQxXn6ozlESsSh1/sMCTF1rL/g==" crossorigin="anonymous"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.1/umd/popper.min.js" integrity="sha512-ubuT8Z88WxezgSqf3RLuNi5lmjstiJcyezx34yIU2gAHonIi27Na7atqzUZCOoY4CExaoFumzOsFQ2Ch+I/HCw==" crossorigin="anonymous"></script>
    <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js" integrity="sha384-B4gt1jrGC7Jh4AgTPSdUtOBvfO8shuf57BaghqFfPlYxofvL8/KUEfYiJOMMV+rV" crossorigin="anonymous"></script>
    <script src="../highlight.pack.js"></script>
    <script>hljs.highlightAll();</script>
  </body>
</html>
